Virtual image display device

ABSTRACT

A virtual image display device has a light guide device in which the half mirror layer (the semi-transmissive reflecting film) of the light guide member is formed on the partial area of the first junction surface, and the second junction surface of the light transmitting member is bonded to the first junction surface in at least the exceptional area. Therefore, it is possible to increase the bonding strength of the first junction surface and the second junction surface, namely the strength of the light guide device composed of the light guide member and the light transmitting member combined with each other even in the case in which the attachment force of the half mirror layer (the semi-transmissive reflecting film) with respect to the first junction surface is not sufficiently strong.

BACKGROUND

1. Technical Field

The present invention relates to a virtual image display device such asa head-mounted display used while worn on the head.

2. Related Art

In recent years, as a virtual image display device such as ahead-mounted display for making formation and observation of a virtualimage possible, there have been proposed various devices, which are atype of guiding the image light from a display element to the pupils ofthe observer using a light guide plate.

In such a virtual display device, in order for overlapping the imagelight and the external light, there has been proposed a see-throughoptical system (see, e.g., JP-A-2010-224473 (Document 1)).

However, in the device described in Document 1, since the see-throughproperty is realized by a pupil division method using a light guideoptical system with an emission opening smaller in size than the pupil,it is difficult to increase the display size of a virtual image.Further, since the light guide optical system smaller in size than thepupil is used, it is difficult to increase the effective pupil diameter(which is the lighting diameter for enabling acquisition of a virtualimage, and is also referred to as an eye ring diameter) in order tocorrespond to individual human pupil distance. Further, since theemission opening and the housing of the light guide optical system arearranged in the physical vicinity of the pupil, a blind area is caused,and it cannot be called a perfect see-through state.

It should be noted that as an optical system for a head-mounted display,there has existed a system provided with a light guide member capable ofmaking a plurality of optical modes different in light guide angleproceed (see JP-T-2008-535001 (Document 2). In such an optical system asdescribed above, it is also possible to adopt a half mirror as a thirdoptical surface on the exit side, and flatten the entire surface byattaching a prism-like member to the light guide member so as to burythe half mirror inside to thereby modify the system into a see-throughlight guide device enabling the observation of the external lightthrough the half mirror.

However, there is a possibility that a strong force is applied to thepart where the light guide member and the prism-like member are bondedto each other, and if the bonding strength between the members is notsufficient, exfoliation is caused in the bonded part, and there is apossibility of damaging the light guide device.

SUMMARY

An advantage of some aspects of the invention is to provide a virtualimage display device equipped with a light guide device, which is formedby bonding a plurality of members, and has a sufficient strength.

A virtual image display device according to an aspect of the inventionincludes (a) an image display device adapted to form an image light, (b)a projection optical system adapted to form a virtual image by the imagelight emitted from the image display device, (c) a light guide memberincluding a light entrance section adapted to take in the image lighthaving passed through the projection optical system, a light guidesection adapted to guide the image light taken in from the lightentrance section using total reflection by a first surface and a secondsurface opposed to each other, and a light exit section adapted to takeout the image light having passed through the light guide section, and(d) a light transmitting member adapted to make observation of externallight possible by being bonded to the light guide member, (e) the lightguide member has a semi-transmissive reflecting film, which bends theimage light and transmits the external light, disposed on a partial areaof a first junction surface to be bonded to the light transmittingmember, and (f) the light transmitting member has a second junctionsurface opposed to the first junction surface including an exceptionalarea excluding the partial area, and bonded to the first junctionsurface with an adhesive in at least the exceptional area. Here, thesemi-transmissive reflecting film is not limited to a metal reflectingfilm, but includes a multilayer film including a dielectric layer and soon, and a hologram element and so on.

In the virtual image display device described above, since thesemi-transmissive reflecting film is formed on the partial area of thefirst junction surface, and the second junction surface of the lighttransmitting member is bonded to the first junction surface in at leastthe exceptional area, it is possible to increase the bonding strengthbetween the first junction surface and the second junction surface,namely the strength of the light guide device composed of the lightguide member and the light transmitting member combined with each other,even in the case in which the attachment force of the semi-transmissivereflecting film with respect to the first junction surface is notsufficiently strong.

According to a specific aspect of the invention, at least one of theexceptional area of the first junction surface and an opposed area ofthe second junction surface corresponding to the exceptional areaincludes a nonsmooth surface having an undulation. In this case, sincethe area of the bonding or junction can be increased due to thenonsmooth surface, the bonding strength between the first junctionsurface and the second junction surface can easily and surely beincreased.

According to another specific aspect of the invention, the nonsmoothsurface is a rough surface provided with a fine undulation by aroughening process. In this case, the process of the nonsmooth surfaceis easy, and the disturbance in the light beam passing through the firstjunction surface and the second junction surface can be suppressed.

According to still another specific aspect of the invention, thenonsmooth surface provided to the first junction surface and thenonsmooth surface provided to the second junction surface fit eachother. In this case, alignment between the light guide member and thelight transmitting member becomes possible via the first junctionsurface and the second junction surface.

According to yet another specific aspect of the invention, the nonsmoothsurface provided to the first junction surface and the nonsmooth surfaceprovided to the second junction surface have undulation shapes reverseto each other. In this case, it is possible to reduce an amount of theadhesive with which the space between the first junction surface and thesecond junction surface is filled.

According to still yet another specific aspect of the invention, in thefirst junction surface of the light guide member, the partial areaadapted to support the semi-transmissive reflecting film is arranged ina central portion of the first junction surface with respect to apredetermined direction, and the exceptional area in a periphery of thesemi-transmissive reflecting film corresponds to a peripheral areasandwiching the partial area on both ends in the predetermineddirection. In the case in which the predetermined direction is avertical direction, the semi-transmissive reflecting film is arranged inthe central portion of the first junction surface in the verticaldirection, and it is possible to dispose the transmitting area formaking the observation of the external light possible without making thesemi-transmissive reflecting film intervene in the upper and lower endsof the first junction surface.

According to further another specific aspect of the invention, the firstjunction surface is bonded to the second junction surface as a whole,and the peripheral area is the nonsmooth surface as a whole.

According to still further another specific aspect of the invention, thelight guide member has the light entrance section, the light guidesection, and the light exit section as an integrated member, the lightentrance section has a third reflecting surface as a plane forming anobtuse angle with respect to either one of the first reflecting surfaceand the second reflecting surface, and the first junction surface of thelight exit section has a fourth reflecting surface as a plane forming anobtuse angle with respect to either one of the first reflecting surfaceand the second reflecting surface. In this case, the image lightreflected by the third reflecting surface of the light entrance sectionis propagated while being totally reflected by the first and secondreflecting surfaces of the light guide section, and is then reflected bythe fourth reflecting surface of the light exit section, and then entersthe eye of the observer as the virtual image. It should be noted that byintegrating the light entrance section, the light guide section, and thelight exit section into an integrated member, it is possible to form thelight guide device with high precision using the injection moldingtechnology.

According to yet further another specific aspect of the invention, thelight guide member, the light transmitting member, and the adhesive areformed of respective materials having roughly the same refractiveindexes. In this case, the disturbance in the light beam in the firstjunction surface and the second junction surface is suppressed tothereby make the accurate observation of the external light possible. Itshould be noted that the phrase “roughly the same refractive indexes”means to allow so minute difference in refractive index that the lightpath is not disturbed although depending on the roughness of the bondingsurface.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a perspective view showing a virtual image display deviceaccording to a first embodiment of the invention.

FIG. 2A is a plan view of a body portion of a first display deviceconstituting the virtual image display device, and FIG. 2B is a frontview of the body portion.

FIG. 3A is a diagram for explaining a structure of a third reflectingsurface in a light entrance section of a light guide member, FIG. 3B isa diagram for explaining a structure of a first reflecting surface in alight guide section of the light guide member, FIG. 3C is a diagram forexplaining a structure of a second reflecting surface in the light guidesection of the light guide member, and FIG. 3D is a diagram forexplaining a structure of a fourth reflecting surface in a light exitsection of the light guide member.

FIG. 4A is a conceptual diagram of developing a light path with respectto a vertical first direction, and FIG. 4B is a conceptual diagram ofdeveloping a light path with respect to a lateral second direction.

FIG. 5 is a plan view for specifically explaining the light path in anoptical system of the virtual image display device.

FIG. 6A is a diagram showing a display surface of a liquid crystaldisplay device, FIG. 6B is a diagram for conceptually explaining thevirtual image of the liquid crystal display device viewed by theobserver, and FIGS. 6C and 6D are diagrams for explaining partial imagesconstituting the virtual image.

FIG. 7 is a perspective view for explaining a bonding process betweenthe light guide member and a light transmissive member.

FIG. 8 is an enlarged cross-sectional view for conceptually explaining ajunction section between the light guide member and the lighttransmissive member.

FIGS. 9A and 9B are diagrams for explaining a part of a virtual imagedisplay device according to a modified example.

FIG. 10 is an enlarged cross-sectional view for conceptually explaininga junction section in a second embodiment of the invention.

FIG. 11 is an enlarged cross-sectional view for conceptually explaininga junction section in a modified example.

FIG. 12 is an enlarged cross-sectional view for conceptually explaininga junction section in a third embodiment of the invention.

FIG. 13A is a cross-sectional view showing a virtual image displaydevice according to a fourth embodiment of the invention, and FIGS. 13Band 13C are a front view and a plan view, respectively, of a light guidedevice.

FIG. 14 is a schematic diagram for explaining a light path of imagelight.

FIG. 15 is a cross-sectional view for explaining a junction sectionincluding a half mirror layer.

FIG. 16A is a cross-sectional view showing a virtual image displaydevice according to a fifth embodiment of the invention, and FIGS. 16Band 16C are a front view and a plan view, respectively, of a light guidedevice.

FIG. 17 is a schematic diagram for explaining a light path of imagelight.

FIG. 18 is a cross-sectional view for explaining a junction sectionincluding a half mirror layer.

FIG. 19 is a conceptual diagram for explaining a virtual image displaydevice according to a modified example.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, some embodiments of the invention will be explained indetail with reference to the accompanying drawings.

A. Exterior Appearance of Virtual Image Display Device

A virtual image display device 100 according to an embodiment shown inFIG. 1 is a head-mounted display having an exterior appearance likespectacles, and is capable of allowing the observer wearing the virtualimage display device 100 to recognize image light of a virtual image,and at the same time allowing the observer to observe the external imagein a see-through manner. The virtual image display device 100 isprovided with an optical panel 110 for covering the front of the eyes ofthe observer, a frame 121 for supporting the optical panel 110, andfirst and second drive sections 131, 132 attached to respective portionseach extending from an end piece to a temple of the frame 121. Here, theoptical panel 110 has a first panel section 111 and a second panelsection 112, and the both panel sections 111, 112 form a plate-like partintegrally coupled on each other at the center thereof. A first displaydevice 100A obtained by combining the first panel section 111 and thefirst drive section 131 located on the left in the drawing is a part forforming a virtual image for the left eye, and functions alone as avirtual image display device. Further, a second display device 100Bobtained by combining the second panel section 112 and the second drivesection 132 located on the right in the drawing is a part for forming avirtual image for the right eye, and functions alone as a virtual imagedisplay device.

B. Structure of Display Devices

As shown in FIG. 2A and so on, the first display device 100A is providedwith the image forming device 10 and a light guide device 20. Here, theimage forming device 10 corresponds to the first drive section 131 shownin FIG. 1, and the light guide device 20 corresponds to the first panelsection 111 shown in FIG. 1. It should be noted that the second displaydevice 100B shown in FIG. 1 has a structure similar to the structure ofthe first display device 100A, which is obtained by simply flipping thestructure of the first display device 100A in a lateral direction, andtherefore, the detailed explanation of the second display device 100Bwill be omitted.

The image forming device 10 has an image display device 11 and aprojection optical system 12. Among these constituents, the imagedisplay device 11 has an illumination device 31 for emittingtwo-dimensional illumination light SL, a liquid crystal display device32 as a transmissive spatial light modulation device, and a drivecontrol section 34 for controlling the operations of the illuminationdevice 31 and the liquid crystal display device 32.

The illumination device 31 has a light source 31 a for generating lightincluding light components of three colors of red, green, and blue, anda backlight light guide section 31 b for diffusing the light from thelight source 31 a to form a light beam having a rectangularcross-section. The liquid crystal display device 32 spatially modulatesthe illumination light SL from the illumination device 31 to therebyform the image light to be the display object such as a moving image.The drive control section 34 is provided with a light source drivecircuit 34 a and a liquid crystal drive circuit 34 b. The light sourcedrive circuit 34 a supplies the light source 31 a of the illuminationdevice 31 with electricity to thereby make it emit the illuminationlight SL with stable luminance. The liquid crystal drive circuit 34 boutputs an image signal or a drive signal to the liquid crystal displaydevice 32 to thereby form the color image light to be an origin of amoving image or a still image in the form of a transmittance pattern. Itshould be noted that it is possible to provide an image processingfunction to the liquid crystal drive circuit 34 b, and it is alsopossible to provide the image processing function to an external controlcircuit. The projection optical system 12 is a collimating lens forconverting the image light emitted from each point on the liquid crystaldisplay device 32 into a light beam in a collimated state.

In the liquid crystal display device 32, the first direction D1corresponds to the vertical Y direction and the second direction D2corresponds to the horizontal X direction. The first direction D1 andthe second direction D2 are perpendicular to a first optical axis AX1passing through the projection optical system 12, and are perpendicularto each other.

The light guide device 20 is obtained by bonding the light guide member21 and a light transmitting member 23 to each other, and forming anoptical member having a tabular shape extending in parallel to the X-Yplane as a whole.

The light guide member 21 out of the light guide device 20 is aprism-like member having a trapezoidal shape in a plan view, and has afirst reflecting surface 21 a, a second reflecting surface 21 b, a thirdreflecting surface 21 c, and a first junction surface 21 j as firstthrough fourth surfaces constituting the side surfaces. Further, thelight guide member 21 also has a first side surface 21 e and a secondside surface 21 f opposed to each other and contiguous to the firstthrough third reflecting surfaces 21 a, 21 b, and 21 c, and the firstjunction surface 21 j. Here, the first and second reflecting surfaces 21a, 21 b extend along the X-Y plane, and are distant from each other asmuch as the thickness “t” of the light guide member 21. Further, thethird reflecting surface 21 c is tilted an acute angle α not larger than45° with respect to the X-Y plane, and the first junction surface 21 jis tilted an acute angle β not larger than 45° with respect to the X-Yplane. In a different point of view, the third reflecting surface 21 chas an obtuse angle η with respect to the second reflecting surface 21b, and the first junction surface 21 j has an obtuse angle ∈ withrespect to the second reflecting surface 21 b. The first optical axisAX1 passing through the third reflecting surface 21 c and the secondoptical axis AX2 passing through the first junction surface 21 j aredisposed in parallel to each other and are distant from each other asmuch as the distance D. It should be noted that, although the detailswill be described below, an edge surface 21 h is disposed between thefirst reflecting surface 21 a and the third reflecting surface 21 c soas to eliminate the ridge. It results that the light guide member 21 hasa polyhedral outer shape composed of seven surfaces including the edgesurface 21 h described above.

The light guide member 21 is for performing light guide using the totalreflection by the first and second reflecting surfaces 21 a, 21 b whichare the first and second surfaces extending oppositely each other, andthere exist directions to be turned by the reflection in the light guideprocess, and directions not to be turned by the reflection in the lightguide process. When considering the image to be guided by the lightguide member 21, the lateral direction to be turned by a plurality oftimes of reflection in the light guide process, namely a confinementdirection DW2, is perpendicular (parallel to the Z axis) to the firstand second reflecting surfaces 21 a, 21 b, and corresponds to the seconddirection D2 of the liquid crystal display device 32 in the case ofdeveloping the light path to the light source side as described later.On the other hand, the vertical direction along which the lightpropagates without being turned by reflection in the light guideprocess, namely a nonconfinement direction DW1, is parallel (parallel tothe Y axis) to the first and second reflecting surfaces 21 a, 21 b, andfurther the third reflecting surface 21 c, and corresponds to the firstdirection D1 of the liquid crystal display device 32 in the case ofdeveloping the light path to the light source side as described later.It should be noted that in the light guide member 21, the principallight guide direction along which the light beam propagating thereinproceeds as a whole is set to −X direction.

The light guide member 21 is made of a resin material exhibiting highlight transmissive property in the visible range. The light guide member21 has an integrated block-like member molded integrally by injectionmolding as a body portion 20 a, and the body portion (the integratedmember) 20 a is formed by, for example, injecting a thermal orphotochemical polymerization resin material inside the molding die andthen causing thermal cure or light cure therein. Although the lightguide member 21 has the body portion 20 a as a base member formed of anintegral-molding product as described above, it is possible tofunctionally divide it into a light entrance section B1, a light guidesection B2, and a light exit section B3.

The light entrance section B1 is a part having a triangular prism shape,and has a light entrance surface IS as a part of the first reflectingsurface 21 a, and the third reflecting surface 21 c opposed to the lightentrance surface IS. The light entrance surface IS is a plane for takingin the image light GL from the image forming device 10 and located onthe reverse side or the observer side, and extends perpendicularly tothe first optical axis AX1 of the projection optical system 12 so as tobe opposed to the projection optical system 12. The third reflectingsurface 21 c has a rectangular outline, and has a mirror layer 25, whichis a reflecting mirror for reflecting the image light GL having passedthrough the light entrance surface IS to thereby guide it inside thelight guide section B2, throughout the roughly entire area inside therectangular outline. The mirror layer 25 is formed by performingdeposition on a tilted surface RS of the light guide member 21 usingevaporation of aluminum or the like.

FIG. 3A is a diagram for explaining the third reflecting surface 21 c,and is a partial enlarged cross-sectional view of a surface portion SP1in the light entrance section B1. The third reflecting surface 21 c hasa mirror layer 25, and is covered by a protective layer 26. The mirrorlayer 25 is a total reflection coating, and is formed by performingdeposition on a tilted surface RS of the body portion 20 a constitutingthe light guide member 21 using evaporation of Al (aluminum) or thelike.

Returning to FIG. 2A and so on, the third reflecting surface 21 c istilted, for example, at an acute angle α of 25° through 27° with respectto the first optical axis AX1 of the projection optical system 12 or theX-Y plane, and folds the image light GL, which enters from the lightentrance surface IS and then proceeds in the +Z direction as a whole, soas to proceed in the −X direction shifted to the −Z direction as awhole, to thereby surely couple the image light GL on the inside of thelight guide section B2. It should be noted that it is also possible toform a hard coat layer in advance as a foundation of the mirror layer25.

The light guide section B2 has the first reflecting surface 21 a and thesecond reflecting surface 21 b, each of which totally reflects the imagelight deflected by the light entrance section B1, as a pair of planesopposed to each other and extending in parallel to the X-Y plane. Thedistance between the first and second reflecting surfaces 21 a, 21 b,namely the thickness t of the light guide member 21, is set to, forexample, about 9 mm. It is assumed here that the first reflectingsurface 21 a is located on the reverse side or the observer side near tothe image forming device 10, and the second reflecting surface 21 b islocated on the obverse side or the external side far from the imageforming device 10. In this case, the surface portion of the firstreflecting surface 21 a is common to the light entrance surface ISdescribed above and the light exit surface OS described later. The firstand second reflecting surfaces 21 a, 21 b are each a total reflectionsurface using the refractive index difference, and no non-transmissivereflecting coat such as a mirror layer is provided to the surfacesthereof.

FIG. 3B is a diagram for explaining the first reflecting surface 21 a,and is a partial enlarged cross-sectional view of a surface portion SP2in the light guide section B2 of the light guide member 21. Further,FIG. 3C is a diagram for explaining the second reflecting surface 21 b,and is a partial enlarged cross-sectional view of a surface portion SP3in the light guide section B2 of the light guide member 21. The firstand second reflecting surfaces 21 a, 21 b are covered by a hard coatlayer 27 in order to prevent damages of the surfaces to thereby preventdegradation in resolution of the picture. The hard coat layer 27 isformed by depositing a coating agent made of resin or the like on a flatsurface FS of the body portion 20 a of the light guide member 21 using adipping process or a spray coating process.

Returning to FIG. 2A, the image light GL having been reflected by thethird reflecting surface 21 c of the light entrance section B1 firstlyenters the first reflecting surface 21 a of the light guide section B2,and is then totally reflected. Subsequently, the image light GL entersthe second reflecting surface 21 b, and is then totally reflected. Bysubsequently repeating the actions described above, the image light isguided in a principal light guide direction on the back side of thelight guide device 20, namely to the −X side where the light exitsection B3 is disposed, as a whole. It should be noted that since thefirst and second reflecting surfaces 21 a, 21 b are not provided withthe non-transmissive or semi-transmissive reflection coat, the externallight or the outside light externally entering the second reflectingsurface 21 b passes through the light guide section B2 at a hightransmittance. In other words, the light guide section B2 is arranged tobe a see-through type through which the external image can be seen.

The light exit section B3 is a part having a triangular prism shape, andhas a light exit surface OS as a part of the first reflecting surface 21a, and the first junction surface 21 j opposed to the light exit surfaceOS. The light exit surface OS is a reverse side plane for emitting theimage light GL toward the eye EY of the observer, and forms a part ofthe first reflecting surface 21 a similarly to the case of the lightentrance surface IS, and extends perpendicularly to the second opticalaxis AX2. The distance D between the second optical axis AX2 passingthrough the light exit section B3 and the first optical axis AX1 passingthrough the light entrance section B1 is set to, for example, 50 mmtaking the width of the head of the observer and so on intoconsideration. The first junction surface 21 j is a roughly rectangulartilted flat surface (a tilted surface RS), and a part thereof isprovided with a fourth reflecting surface 21 d for reflecting the imagelight GL, which has entered there via the first and second reflectingsurfaces 21 a, 21 b, to thereby emit it to the outside of the light exitsection B3.

The fourth reflecting surface 21 d has a half mirror layer 28. The halfmirror layer 28 is a reflecting film (i.e., a semi-transmissivereflecting film) having a light transmissive property. The half mirrorlayer (the semi-transmissive reflecting film) 28 is formed on a partialarea PA0 of the first junction surface 21 j rather than the entire firstjunction surface 21 j. The partial area PA0 to be provided with the halfmirror layer 28 out of the first junction surface 21 j is disposed on acentral side with respect to the non-confinement direction DW1 as thevertical direction, and is sandwiched by a pair of peripheral areas PA1,PA2 on both of the upper and lower ends. Further, on the −X side of thepartial area PA0, there exists a back side area PA3 not provided withthe half mirror layer 28. An exceptional area PA composed of theseperipheral areas PA1, PA2, and the back side area PA3 collected witheach other is an area where the half mirror layer 28 as the fourthreflecting surface 21 d does not exist, and transmits the image light GLand so on with no substantial change. The half mirror layer 28 is formedby depositing a metal reflecting film or a dielectric multilayer film onthe partial area PA0 out of the first junction surface 21 j of the bodyportion 20 a constituting the light guide member 21. The reflectance ofthe half mirror layer 28 with respect to the image light GL is set to benot lower than 10% and not higher than 50% in the assumed incident anglerange of the image light GL from the view point of making thesee-through observation of the external light GL′ easy. The reflectanceof the half mirror layer 28 with respect to the image light GL in aspecific example is set to, for example, 20%, and the transmittance withrespect to the image light GL is set to, for example, 80%.

FIG. 3D is a diagram for explaining a structure of the fourth reflectingsurface 21 d and the periphery thereof. Here, between the fourthreflecting surface 21 d of the light guide member 21 and the secondjunction surface 23 c of the light transmitting member 23, moreprecisely between the half mirror layer 28 and the second junctionsurface 23 c, there is formed a bonding layer CC with an adhesive forbonding the light guide member 21 and the light transmitting member 23.The bonding layer CC has the refractive index roughly equal to those ofthe body portion 20 a of the light guide member 21 and a bulk materialof the light transmitting member 23 to thereby prevent the light passingthrough the light guide member 21, the light transmitting member 23, andthe interfaces between these members and the bonding layer CC from thelight guide member 21 to the light transmitting member 23 from beingunnecessarily reflected by the interfaces.

Returning to FIG. 2A and so on, the fourth reflecting surface 21 d orthe first junction surface 21 j is tilted, for example, at an acuteangle α of 25° through 27° with respect to the second optical axis AX2perpendicular to the first reflecting surface 21 a or the X-Y plane, andthe image light GL, which has entered there via the first and secondreflecting surfaces 21 a, 21 b of the light guide section B2, ispartially reflected to thereby deflect it so as to proceed toward the −Zdirection as a whole using the half mirror layer 28 described above, andis thus transmitted through the light exit surface OS. It should benoted that the component of the image light transmitted through thefourth reflecting surface 21 d enters the light transmitting member 23,and is not used for forming the picture.

As shown in FIG. 2B, an effective area EA through which the image lightGL is transmitted out of the light guide member 21 has a vertically longshape in comparison on the light entrance section B1 side, and has ahorizontally long shape in comparison on the light exit section B3 side.The fourth reflecting surface 21 d or the half mirror layer 28 is a partof the first junction surface 21 j, but is formed so as to correspond tothe effective area EA of the image light GL, and covers the effectivearea EA, and the image light GL guided by the light guide member 21passes through the light entrance section B1 without loss, and thenenters the eye EY of the observer. As described above, the half mirrorlayer 28 has a horizontally long contour, but is arranged to correspondto the horizontally long contour of an image forming area AD of theliquid crystal display device 32.

The light transmitting member 23 is formed of the same material as thatof the body portion 20 a of the light guide member 21 to thereby havethe same refractive index as that of the body portion 20 a, and has afirst surface 23 a, a second surface 23 b, and the second junctionsurface 23 c. The first and second surfaces 23 a, 23 b extend along theX-Y plane. Further, the second junction surface 23 c is tilted withrespect to the X-Y plane, and is disposed so as to be opposed inparallel to the first junction surface 21 j or the fourth reflectingsurface 21 d of the light guide member 21. In other words, the lighttransmitting member 23 is arranged to have a member WP having a wedgeshape sandwiched between the second surface 23 b and the second junctionsurface 23 c. The light transmitting member 23 is formed of a resinmaterial exhibiting high light transmissive property in the visiblerange similarly to the light guide member 21. The light transmittingmember 23 is a block-like integrated member formed by an injectionmolding process, and is formed by, for example, injecting a thermal orphotochemical polymerization resin material inside the molding die andthen causing thermal cure or light cure therein.

In the light transmitting member 23, the first surface 23 a is disposedon an extended plane of the first reflecting surface 21 a provided tothe light guide member 21, and is located on the reverse side near tothe eye EY of the observer, and the second surface 23 b is disposed onan extended plane of the second reflecting surface 21 b provided to thelight guide member 21, and is located on the obverse side far from theeye EY of the observer. The second junction surface 23 c is arectangular light transmitting surface to be bonded to the firstjunction surface 21 j of the light guide member 21 with an adhesive. Theangle formed between the first surface 23 a and the second junctionsurface 23 c described above is arranged to be equal to the angle ∈formed between the second reflecting surface 21 b and the first junctionsurface 21 j of the light guide member 21, and the angle formed betweenthe second surface 23 b and the second junction surface 23 c is arrangedto be equal to the angle β formed between the first reflecting surface21 a and the third reflecting surface 21 c of the light guide member 21.

The light transmitting member 23 and the light guide member 21constitute a see-through section B4 in the junction section of the bothmembers and the vicinity thereof. Specifically, the first and secondsurfaces 23 a, 23 b are not provided with a reflection coat such as amirror layer, and therefore, transmit the external light GL′ at a hightransmittance similarly to the light guide section B2 of the light guidemember 21. Although the second junction surface 23 c can also transmitthe external light GL′ at a high transmittance, since the half mirrorlayer 28 exists in an area corresponding to the fourth reflectingsurface 21 d of the light guide member 21, the external light GL′passing through the second junction surface 23 c fades, for example, by20%. In other words, it results that the observer observes the lightobtained by overlapping the image light GL having faded to 20% and theexternal light GL′ having faded to 80%.

C. General Outline of Light Path of Image Light

FIG. 4A is a diagram for explaining the light path in the firstdirection D1 corresponding to a vertical cross-sectional surface CS1 ofthe liquid crystal display device 32. In the vertical cross-sectionalsurface along the first direction D1, namely the Y-Z plane (the Y′-Z′plane after the development), out of the image light having been emittedfrom the liquid crystal display device 32, a component emitted from anupper end side (+Y side) of the display area 32 b indicated by thedashed-dotted line in the drawing is referred to as image light GLa, anda component emitted from the lower end side (−Y side) of the displayarea 32 b indicated by the dashed-two dotted line in the drawing isreferred to as image light GLb.

The image light GLa on the upper side is converted by the projectionoptical system 12 into a parallel light beam, and enters the eye EY ofthe observer along the developed optical axis AX′ through the lightentrance section B1, the light guide section B2, and the light exitsection B3 of the light guide member 21 in a state of the parallel lightbeam from above at an angle φ₁ in a tilted manner. On the other hand,the image light GLb on the lower side is converted by the projectionoptical system 12 into a parallel light beam, and enters the eye EY ofthe observer along the developed optical axis AX′ through the lightentrance section B1, the light guide section B2, and the light exitsection B3 of the light guide member 21 in a state of the parallel lightbeam from beneath at an angle φ₂ (|φ₂|=|φ₁|) in a tilted manner. Theangles φ₁, φ₂ described above correspond respectively to upper and lowerhalf field angles, and are set to, for example, 6.5°.

FIG. 4B is a diagram for explaining the light path in the seconddirection D2 corresponding to a horizontal cross-sectional surface CS2of the liquid crystal display device 32. In the horizontalcross-sectional surface CS2 along the second direction D2, namely theX-Z plane (the X′-Z′ plane after the development), out of the imagelight having been emitted from the liquid crystal display device 32, acomponent emitted from a first display point P1 on the right end side(+X side) toward the display area 32 b indicated by the dashed-dottedline in the drawing is referred to as image light GL1, and a componentemitted from a second display point P2 on the left end side (−X side)toward the display area 32 b indicated by the dashed-two dotted line inthe drawing is referred to as image light GL2.

The image light GL1 from the first display point P1 on the right side isconverted by the projection optical system 12 into a parallel lightbeam, and enters the eye EY of the observer along the developed opticalaxis AX′ through the light entrance section B1, the light guide sectionB2, and the light exit section B3 of the light guide member 21 in astate of the parallel light beam from the right at an angle θ₁ in atilted manner. Meanwhile, the image light GL2 from the second displaypoint P2 on the left side is converted by the projection optical system12 into a parallel light beam, and enters the eye EY of the observeralong the developed optical axis AX′ through the light entrance sectionB1, the light guide section B2, and the light exit section B3 of thelight guide member 21 in a state of the parallel light beam from theleft at an angle θ₂ (|θ₂|=|θ₁|) in a tilted manner. The angles θ₁, θ₂described above correspond respectively to right and left half fieldangles, and are set to, for example, 10°.

It should be noted that regarding the lateral direction of the seconddirection D2 or the confinement direction DW2, since the image lightsGL1, GL2 are turned in the light guide member 21 by reflection, and thenumber of times of reflection is different therebetween, each of theimage lights GL1, GL2 is expressed in the light guide member 21 in adiscontinuous manner. Further, regarding the eye EY of the observer, theviewing direction is flipped vertically compared to the case shown inFIG. 2A. As a result, although the screen is flipped horizontally as awhole regarding the lateral direction, the right half image of theliquid crystal display device 32 and the left half image of the liquidcrystal display device 32 become continuously connected to each otherwithout a displacement by processing the light guide member 21 with highaccuracy as described later in detail. It should be noted that theemission angle θ₁′ of the image light GL1 on the right side and theemission angle θ₂′ of the image light GL2 on the left side are setdifferently taking the fact that the both image lights GL1, GL2 aredifferent from each other in the number of times of reflection in thelight guide member 21 into consideration.

According to the configuration described above, the image lights GLa,GLb, GL1, and GL2 entering the eye EY of the observer are arranged to bethe virtual image from infinity, the picture formed on the liquidcrystal display device 32 is erected with respect to the vertical firstdirection D1 or the non-confinement direction DW1, and the pictureformed on the liquid crystal display device 32 is inverted with respectto the horizontal second direction D2 or the confinement direction DW2.

D. Light Path of Image Light Regarding Lateral Direction

FIG. 5 is a cross-sectional view for explaining the specific light pathin the first display device 100A. The projection optical system 12 hasthree lenses L1, L2, and L3.

Image lights GL11, GL12 from the first display point P1 on the rightside of the liquid crystal display device 32 are converted into aparallel light beam by passing through the lenses L1, L2, and L3 of theprojection optical system 12, and then enter the light entrance surfaceIS of the light guide member 21. The image lights GL11, GL12 guided intothe light guide member 21 repeat total reflection on the first andsecond reflecting surfaces 21 a, 21 b at the same angle, and are finallyemitted from the light exit surface OS as a parallel light beam.Specifically, the image lights GL11, GL12 are reflected by the thirdreflecting surface 21 c of the light guide member 21 as a parallel lightbeam, then enter the first reflecting surface 21 a of the light guidemember 21 at a first reflection angle γ1, and are then totally reflected(first total reflection). Subsequently, the image lights GL11, GL12enter the second reflecting surface 21 b to be totally reflected (secondtotal reflection), and then enter the first reflecting surface 21 aagain to be totally reflected (third total reflection) in the state ofkeeping the first reflection angle γ1. As a result, the image lightsGL11, GL12 are totally reflected by the first and second reflectingsurfaces 21 a, 21 b three times in total, and then enter the fourthreflecting surface 21 d. The image lights GL11, GL12 are reflected bythe fourth reflecting surface 21 d at an angle equal to the angle withrespect to the third reflecting surface 21 c, and are then emitted fromthe light exit surface OS at an angle θ₁ with respect to the directionof the second optical axis AX2 perpendicular to the light exit surfaceOS as the parallel light beam.

Image lights GL21, GL22 from the second display point P2 on the leftside of the liquid crystal display device 32 are converted into aparallel light beam by passing through the lenses L1, L2, and L3 of theprojection optical system 12, and then enter the light entrance surfaceIS of the light guide member 21. The image lights GL21, GL22 guided intothe light guide member 21 repeat total reflection on the first andsecond reflecting surfaces 21 a, 21 b at the same angle, and are finallyemitted from the light exit surface OS as a parallel light beam.Specifically, the image lights GL21, GL22 are reflected by the thirdreflecting surface 21 c of the light guide member 21 as a parallel lightbeam, then enter the first reflecting surface 21 a of the light guidemember 21 at a second reflection angle γ2 (γ2<γ1), and are then totallyreflected (first total reflection). Subsequently, the image lights GL21,GL22 enter the second reflecting surface 21 b to be totally reflected(second total reflection), then enter the first reflecting surface 21 aagain to be totally reflected (third total reflection), then enter thesecond reflecting surface 21 b again to be totally reflected (fourthtotal reflection), and then enter the first reflecting surface 21 aagain to be totally reflected (fifth total reflection) in the state ofkeeping the second reflection angle γ2. As a result, the image lightsGL21, GL22 are totally reflected on the first and second reflectingsurfaces 21 a, 21 b five times in total, and then enter the fourthreflecting surface 21 d. The image lights GL21, GL22 are reflected bythe fourth reflecting surface 21 d at an angle equal to the angle withrespect to the third reflecting surface 21 c, and are then emitted fromthe light exit surface OS at an angle θ₂ with respect to the directionof the second optical axis AX2 perpendicular to the light exit surfaceOS as the parallel light beam.

In FIG. 5, there are drawn an imaginary first surface 121 acorresponding to the first reflecting surface 21 a when developing thelight guide member 21, and an imaginary second surface 121 bcorresponding to the second reflecting surface 21 b when developing thelight guide member 21. By developing the light guide member 21 asdescribed above, it is understood that the image lights GL11, GL12 fromthe first display point P1 pass through an entrance equivalent surfaceIS′ corresponding to the light entrance surface IS, then pass throughthe first surface 121 a twice and the second surface 121 b once, and arethen emitted from the light exit surface OS to thereby enter the eye EYof the observer, and the image lights GL21, GL22 from the second displaypoint P2 pass through an entrance equivalent surface IS″ correspondingto the light entrance surface IS, then pass through the first surface121 a three times and the second surface 121 b twice, and are thenemitted from the light exit surface OS to thereby enter the eye EY ofthe observer. In a different point of view, it results that the observermakes the observation while making the lenses L3 of the projectionoptical system 12, which exist in the vicinities of the two entranceequivalent surfaces IS′, IS″ located differently from each other,overlap each other.

FIG. 6A is a diagram for conceptually explaining a display surface ofthe liquid crystal display device 32, FIG. 6B is a diagram forconceptually explaining the virtual image of the liquid crystal displaydevice 32 viewed by the observer, and FIGS. 6C and 6D are diagrams forexplaining partial images constituting the virtual image. A rectangularimage forming area AD provided to the liquid crystal display device 32shown in FIG. 6A is observed as a virtual image display area AI shown inFIG. 6B. In the left part of the virtual image display area AI, there isformed a first projection image IM1 corresponding to a part located in arange from the center to the right side of the image forming area AD ofthe liquid crystal display device 32, and the first projection image IM1is formed as a partial image lacking the right part as shown in FIG. 6C.Further, in the right part of the virtual image display area AI, asecond projection image IM2 corresponding to a part located in a rangefrom the center to the left side of the image forming area AD of theliquid crystal display device 32 is formed as a virtual image, and thesecond projection image IM2 is formed as a partial image lacking theleft part as shown in FIG. 6D.

A first partial area A10 for forming only the first projection image(the virtual image) IM1 out of the liquid crystal display device 32shown in FIG. 6A includes, for example, the first display point P1 atthe right end of the liquid crystal display device 32, and emits theimage lights GL11, GL12 to be totally reflected in the light guidesection B2 of the light guide member 21 three times in total. A secondpartial area A20 for forming only the second projection image (thevirtual image) IM2 out of the liquid crystal display device 32 includes,for example, the second display point P2 at the left end of the liquidcrystal display device 32, and emits the image lights GL21, GL22 to betotally reflected in the light guide section B2 of the light guidemember 21 five times in total. The image light from a band SA sandwichedby the first and second partial areas A10, A20 in the central area ofthe image forming area AD of the liquid crystal display device 32, andextending to form a vertically long shape forms an overlapping image SIshown in FIG. 6B. In other words, it results that the image light fromthe band SA of the liquid crystal display device 32 forms the firstprojection image IM1 formed by the image lights GL11, GL12 totallyreflected in the light guide section B2 three times in total and thesecond projection image IM2 formed by the image lights GL21, GL22totally reflected in the light guide section B2 five times in total, andthe projection images IM1, IM2 overlap each other on the virtual imagedisplay area AI. If the processing of the light guide member 21 isprecise and the light beam accurately collimated is formed by theprojection optical system 12, the displacement and blur due to theoverlap of the two projection images IM1, IM2 can be prevented withrespect to the overlapping image SI.

E. Junction of Light Guide Member and Light Transmitting Member

As shown in FIG. 7, when bonding the light guide member 21 and the lighttransmitting member 23 to each other, the half mirror layer 28 is formedin advance on the partial area PA0 in the first junction surface 21 j ofthe light guide member 21. Subsequently, an ultraviolet curableadhesive, for example, is applied on the half mirror layer 28 and theexceptional area PA in the periphery thereof, and is then spread.Further, the second junction surface 23 c of the light transmittingmember 23 is disposed so as to face the half mirror layer 28 and theexceptional area PA, and then the curing light as the ultraviolet lightis applied between the first and second junction surfaces 21 j, 23 cwhile pressing them with an appropriate force. Thus, the adhesivebetween the first and second junction surfaces 21 j, 23 c cures tothereby complete the bonding between the light guide member 21 and thelight transmitting member 23. On this occasion, since not only the spacebetween the half mirror layer 28 and the second junction surface 23 cbut also the space between the exceptional area PA and the secondjunction surface 23 c are filled with the adhesive, and the bondinglayer CC is formed by the curing of the adhesive (see FIG. 3D), thebonding strength between the light guide member 21 and the lighttransmitting member 23 increases.

FIG. 8 is an enlarged cross-sectional view for conceptually explainingthe junction section between the light guide member 21 and the lighttransmitting member 23. The body portion 20 a of the light guide member21 and the body portion 20 b of the light transmitting member 23 arecoupled on each other by the bonding layer CC formed between the firstand second junction surfaces 21 j, 23 c. Here, regarding the exceptionalarea PA in the periphery, the first and second junction surfaces 21 j,23 c with mirrored surfaces are directly bonded to each other via thebonding layer CC, and therefore, the necessary bonding strength can beprovided with relative ease. In contrast, regarding the partial area PA0in the central portion, since the half mirror layer 28 exists betweenthe first junction surface 21 j and the bonding layer CC, and the halfmirror layer 28 is formed by evaporation coating and provides relativelyweak attachment force, it is relatively difficult to provide thenecessary bonding strength. As a result, the light guide member 21 andthe light transmitting member 23 are tightly bonded to each other mainlyin the exceptional area PA in the periphery, and thus the sufficientlyhigh strength of the light guide device 20 composed of the light guidemember 21 and the light transmitting member 23 can be obtained.

It should be noted that the half mirror layer (semi-transmissivereflecting film) 28 shown in the drawing is arranged to have a sandwichstructure having a metal reflecting film 28 a, a first dielectricmultilayer film 28 b, and a second dielectric multilayer film 28 cstacked so that the metal reflecting film 28 a comes the center. Themetal reflecting film 28 a is formed of a material such as Ag or Al. Thefirst dielectric multilayer film 28 b on the lower side and the seconddielectric multilayer film 28 c on the upper side are each a film formedby laminating, for example, more than a few transparent dielectriclayers, and improve the angular characteristic and so on of the metalreflecting film 28 a. It should be noted that these dielectricmultilayer films 28 b, 28 c can also be eliminated.

According to the virtual image display device 100 of the embodimentdescribed above, since the half mirror layer (the semi-transmissivereflecting film) 28 of the light guide member 21 is formed on thepartial area PA0 of the first junction surface 21 j, and the secondjunction surface 23 c of the light transmitting member 23 is tightlybonded to the first junction surface 21 j in at least the exceptionalarea PA in the light guide device 20, it is possible to increase thebonding strength of the first junction surface 21 j and the secondjunction surface 23 c, namely the strength of the light guide device 20composed of the light guide member 21 and the light transmitting member23 combined with each other even in the case in which the attachmentforce of the half mirror layer (the semi-transmissive reflecting film)28 with respect to the first junction surface 21 j is not sufficientlystrong.

Although it is assumed hereinabove that the number of times of totalreflection of the image lights GL11, GL12 emitted from the first partialarea A10 including the first display point P1 on the right side of theliquid crystal display device 32 by the first and second reflectingsurfaces 21 a, 21 b is three in total, and the number of times of totalreflection of the image lights GL21, GL22 emitted from the secondpartial area A20 including the second display point P2 on the left sideof the liquid crystal display device 32 by the first and secondreflecting surfaces 21 a, 21 b is five in total, the numbers of times oftotal reflection can arbitrarily be changed. Specifically, it is alsopossible to set the number of times of total reflection of the imagelights GL11, GL12 to five in total and to set the number of times oftotal reflection of the image lights GL21, GL22 to seven in total byadjusting the outer shape (i.e., the thickness t, the distance D, andthe acute angles α, β) of the light guide member 21. Further, althoughit is assumed hereinabove that the numbers of times of total reflectionof the image lights GL11, GL12, GL21, and GL22 are odd numbers, if thelight entrance surface IS and the light exit surface OS are disposed onthe respective sides opposite to each other, namely if the light guidemember 21 is formed to have a parallelogram shape in a plane view, thenumbers of times of total reflection of the image lights GL11, GL12,GL21, and GL22 are even numbers.

FIG. 9A is a diagram for explaining a light guide member 621 obtained bymodifying the light guide member 21 shown in FIG. 2A. Although in theexplanation described hereinabove it is assumed that the image lightpropagating in the light guide member 21 is totally reflected by thefirst and second reflecting surfaces 21 a, 21 b at two reflectionangles, and propagate in two modes, it is also possible to allow threecomponents of the image light GL31, GL32, and GL33 to be totallyreflected at respective reflection angles γ1, γ2, and γ3 (γ1>γ2>γ3) asin a modified example of the light guide member 621 shown in FIG. 9A. Inthis case, the image light GL emitted from the liquid crystal displaydevice 32 propagates in three modes, and is combined at the position ofthe eye EY of the observer and is recognized as a virtual image. In thiscase, as shown in FIG. 9B, a projection image IM21 totally reflectedthree times in total is formed in the left part of the effective displayarea A0, a projection image IM22 totally reflected five times in totalis formed in the central part of the effective display area A0, and aprojection image IM23 totally reflected seven times in total is formedin the right part of the effective display area A0.

Further, it is also possible to dispose an optical element such as alens so as to face the light exit surface OS of the light guide member21 shown in FIG. 2B. Alternatively, the half mirror layer 28 can bereplaced with a hologram sheet coated with a protective layer. In thiscase, a device having a high coherent property is used as theillumination device 31, and a diffractive sheet of a laminate type forindividually processing a three-color image, for example, formed by theliquid crystal display device 32 is used as the hologram sheet.

Second Embodiment

Hereinafter, a virtual image display device according to a secondembodiment will be explained. It should be noted that the virtual imagedisplay device according to the present embodiment is a modified exampleof the virtual image display device 100 according to the firstembodiment, and is assumed to be the same as the virtual image displaydevice 100 according to the first embodiment unless particularlyexplained.

As shown in FIG. 10, in the case of the second embodiment, in theexceptional area PA in the first junction surface 221 j of the lightguide member 21, there are formed rough surfaces SR each having fineundulations 41 as nonsmooth surfaces. The rough surfaces (the nonsmoothsurfaces) SR are formed by, for example, performing a roughening processin advance on a transcription surface of the molding die of the bodyportion 20 a. Further, the rough surfaces SR can also be formed byperforming a roughening process or a surface modification process suchas sandblast or etching by a chemical or the like after, for example,molding of the body portion 20 a.

The depth of the fine undulations 41 constituting each of the roughsurfaces SR is set to, for example, about several μm through severaltens μm. It should be noted that although exaggerated in the drawing,the thickness of the half mirror layer (the semi-transmissive reflectingfilm) 28 is about, for example, several μm, and the thickness of thebonding layer CC is about, for example, 50 μm. In a specific example,the difference in refractive index between the body portion 20 a of thelight guide member 21 and the bonding layer CC is set to be equal to orsmaller than, for example, 0.02. Thus, it is possible to prevent theexternal light GL′ from being disturbed by the existence of the roughsurfaces SR.

FIG. 11 is a cross-sectional view for explaining a modified example ofthe light guide member 21 shown in FIG. 10. In the case shown in thedrawing, in the opposed areas PA4 corresponding to the exceptional areaPA of the first junction surface 221 j out of the second junctionsurface 223 c of the light transmitting member 23, there are formedrough surfaces SR each having fine undulations as nonsmooth surfaces.Also in this case, if the difference in refractive index between thebody portion 20 b of the light transmitting member 23 and the bondinglayer CC is small, it is possible to prevent the external light GL′ frombeing disturbed by the existence of the rough surfaces (the nonsmoothsurfaces) SR.

It should be noted that although not shown in the drawings, it is alsopossible to form the entire second junction surface 223 c to be therough surface SR. Further, it is also possible to form only the secondjunction surface 223 c to be the rough surface SR, and to form the firstjunction surface 221 j of the light guide member 21 to be the firstjunction surface 21 j as the smooth surface shown in FIG. 8.

According to the virtual image display device 100 according to thesecond embodiment, since at least one of the first junction surface 221j and the exceptional area PA of the second junction surface 223 cincludes the rough surface SR as the nonsmooth surface having theundulations in the light guide device 20, it is possible to increase thearea of bonding or junction due to the rough surface (the nonsmoothsurface) SR to thereby easily and surly increase the bonding strengthbetween the first junction surface 221 j and the second junction surface223 c.

Third Embodiment

Hereinafter, a virtual image display device according to a thirdembodiment will be explained. It should be noted that the virtual imagedisplay device according to the present embodiment is a modified exampleof the virtual image display device 100 according to the firstembodiment, and is assumed to be the same as the virtual image displaydevice 100 according to the first embodiment unless particularlyexplained.

As shown in FIG. 12, in the case of the third embodiment, in theexceptional area PA in the first junction surface 321 j of the lightguide member 21, there are formed first fitting shapes SF1, each ofwhich is a relatively coarse undulation shape, as the nonsmooth surfaceshaving undulations. Each of the first fitting shapes (the nonsmoothsurfaces) SF1 can be formed by arranging, for example, a number ofV-grooves, which are linearly extending undulations, in a directionalong the shorter dimension of the groove. On the other hand, in theopposed areas PA4 corresponding to the exceptional area PA of the firstjunction surface 321 j out of the second junction surface 323 c of thelight transmitting member 23, there are formed second fitting shapesSF2, which are relatively coarse undulation shapes, as the nonsmoothsurfaces. These second fitting shapes SF2 are each formed to have ashape obtained by reversing the undulation shape of the correspondingone of the first fitting shapes SF1. In other words, each of the firstfitting shapes SF1 and the corresponding one of the second fittingshapes SF2 have the respective shapes reversed from each other havingthe reversed undulation patterns. Specifically, each of the secondfitting shapes SF2 can be formed by arranging, for example, a number ofridge-like sections, each of which has a triangular cross-sectionalshape and extends linearly, in a direction along the shorter dimensionof the ridge-like section.

It should be noted that the first fitting shapes SF1 each can be formedto have convex sections and concave sections each having a pyramid shapeand arranged two-dimensionally, and the second fitting shapes SF2 eachcan also be formed to have convex sections and concave sections eachhaving a pyramid shape and arranged two-dimensionally as the reversedshape of the corresponding one of the first fitting shapes SF1.

According to the virtual image display device 100 of the thirdembodiment, a precise alignment between the light guide member 21 andthe light transmitting member 23 becomes possible by fitting the firstfitting shapes (the nonsmooth surfaces) SF1 of the first junctionsurface 321 j and the second fitting shapes (the nonsmooth surfaces) SF2of the second junction surface 323 c.

Fourth Embodiment

Hereinafter, a virtual image display device according to a fourthembodiment will be explained. It should be noted that the virtual imagedisplay device according to the present embodiment is a modified exampleof the virtual image display device 100 according to the firstembodiment, and is assumed to be the same as the virtual image displaydevice 100 according to the first embodiment unless particularlyexplained.

The virtual image display device 100 shown in FIGS. 13A through 13C isprovided with the image forming device 10 and a light guide device 420as a set. The light guide device 420 is provided with a light guide bodymember 21 a, an angle conversion section 423, and a light transmittingbody member 23 s. It should be noted that FIG. 13A corresponds to theA-A cross-section of the light guide device 420 shown in FIG. 13B.

An overall appearance of the light guide body member 21 s is a flatplate extending in parallel to the X-Y plane in the drawing. Further,the light guide body member 21 s has the first reflecting surface 21 a,the second reflecting surface 21 b, and the third reflecting surface 21c as the side surfaces, and further has the first junction surface 21 jdescribed later (see FIG. 14). Further, the light guide body member 21 salso has a first side surface 21 e and a second side surface 21 fopposed to each other and contiguous to the first, second, and thirdreflecting surfaces 21 a, 21 b, and 21 c. Further, the light guide bodymember 21 s has a structure in which a prism section PS is disposed atone end thereof in the longitudinal direction, and the angle conversionsection 423 composed of a number of mirrors is connected thereto at theother end thereof in the longitudinal direction.

The body portion 20 a, which is a base or a substrate of the light guidebody member 21 s, is formed of a light transmissive resin material orthe like, and has the light entrance surface IS, which takes in theimage light from the image forming device 10, disposed on the flatsurface on the reverse side parallel to the X-Y plane and opposed to theimage forming device 10. The body portion 20 a has a rectangular tiltedsurface RS as a side surface of the prism section PS besides the lightentrance surface IS, and on the tilted surface RS, there is formed amirror layer 25 so as to cover the tilted surface RS. Here, the mirrorlayer 25 cooperates with the tilted surface RS to thereby function asthe third reflecting surface 21 c disposed in the tilted state withrespect to the light entrance surface IS. The third reflecting surface21 c bends the image light, which enters the light entrance surface ISand proceeds in the +Z direction as a whole, so as to proceed in the −Xdirection deflected to the −Z direction as a whole to thereby surelycombine the image light within the body portion 20 a.

The first and second reflecting surfaces 21 a, 21 b of the light guidebody member 21 s each totally reflect the image light bent by the prismsection PS as a pair of planes, which are the principal surfaces of thebody portion 20 a shaped like a flat plate, opposed to each other, andextend in parallel to the X-Y plane. The image light having beenreflected by the third reflecting surface 21 c firstly enters the firstreflecting surface 21 a, and is then totally reflected. Subsequently,the image light enters the second reflecting surface 21 b, and is thentotally reflected. By subsequently repeating the actions describedabove, the image light is guided to the back side of the light guidebody member 21 s, namely the −X side where the angle conversion section423 is disposed.

As shown in FIG. 13C, in the light guide body member 21 s, the thirdreflecting surface 21 c and the light entrance surface IS describedlater function as the light entrance section B1. Further, the bodyportion 20 a sandwiched between the first and second reflecting surfaces21 a, 21 b of the light guide body member 21 s and the angle conversionsection 423 described later function as the light guide section B2. Itshould be noted that the angle conversion section 423 functions as thelight exit section B3.

The angle conversion section 423 is formed on the back side (−X side) ofthe light guide body member 21 s along extended planes of the first andsecond reflecting surfaces 21 a, 21 b. Here, the back side end portionof the body portion 20 a forms a part of the angle conversion section423. The angle conversion section 423 has a number of half mirror layers28 tilted with respect to the first and second reflecting surfaces 21 a,21 b, and arranged in parallel to each other at regular intervals. Theangle conversion section 423 reflects the image light, which has beeninput thereto via the first and second reflecting surfaces 21 a, 21 b ofthe light guide member 421, at a predetermined angle to thereby bend ittoward the eye EY of the observer via the light exit surface OS. Inother words, the angle conversion section 423 converts the angle of theimage light.

The light transmitting body member 23 s is a part formed by extendingthe angle conversion section 423 toward the back side (−X side), and isa plate-like member similarly to the light guide body member 21 s of thelight guide member 421.

In the above configuration, the whole or an entrance side part of theangle conversion section 423 functions as the light guide member whencombined with the light guide body member 21 s. Further, the whole or aback side part of the angle conversion section 423 functions as thelight transmitting member when combined with the light transmitting bodymember 23 s.

The image light emitted from the image forming device 10 and thenentering the light guide body member 21 s from the light entrancesurface IS is evenly reflected and bent by the third reflecting surface21 c, then proceeds substantially along the optical axis AX in acondition of having certain spread while being totally reflected in thefirst and second reflecting surfaces 21 a, 21 b of the light guide bodymember 21 s in a repeated manner, and is then further bent in the angleconversion section 423 at an appropriate angle to thereby be in thestate ready to be taken out, and is then finally emitted to the outsidefrom the light exit surface OS attached to the angle conversion section423. The image light emitted to the outside from the light exit surfaceOS enters the eye EY of the observer as the virtual image light.

The light path of the image light in the light guide device 420 willhereinafter be explained. It should be noted that the light guide device420 in the fourth embodiment functions similarly to the light guidedevice 20 shown in FIG. 1A with respect to the vertical first directionD1 (the Y direction). In contrast, the light guide device 420 isarranged to guide the image light with a number of propagation modeswith respect to the horizontal second direction D2 (the X direction),and is different from the light guide device 20 shown in FIG. 2A forguiding the image light with the two propagation modes.

As shown in FIG. 13A, it is assumed that, out of the image light outputfrom the liquid crystal display device (the image light forming section)32 of the image display device 11, the component emitted from thecentral portion of the emission surface 32 a indicated by the dottedline is image light GL41, the component emitted from the right side (+Xside) of the sheet of the emission surface 32 a indicated by thedashed-dotted line is image light GL42, and the component emitted fromthe left side (−X side) of the sheet of the emission surface 32 aindicated by the dashed-two dotted line is image light GL43.

The principal components of the respective image lights GL41, GL42, andGL43 having passed through the projection optical system 12 enter fromthe light entrance surface IS of the light guide body member 21 s, andthen repeat the total reflection on the first and second reflectingsurfaces 21 a, 21 b at respective angles different from each other.Specifically, among the image lights GL41, GL42, and GL43, the imagelight GL41 emitted from the central portion of the emission surface 32 aof the liquid crystal display device (the image light forming section)32 enters the light entrance surface IS as a parallel light beam afterpassing through the projection optical system 12, and is then reflectedby the third reflecting surface 21 c, and then enters the firstreflecting surface 21 a of the light guide body member 21 s at astandard reflection angle γ₀, and is then totally reflected.Subsequently, the image light GL41 repeats the total reflection on thefirst and second reflecting surfaces 21 a, 21 b in a condition ofkeeping the standard reflection angle γ₀. The image light GL41 istotally reflected by the first and second reflecting surfaces 21 a, 21 bN times (N denotes a natural number), and then reaches the centralportion 23 k of the angle conversion section 423. The image light GL41reflected by the central portion 23 k is emitted from the light exitsurface OS in the direction of the optical axis AX perpendicular to thelight exit surface OS or the X-Y plane as a parallel light beam.

The image light GL42 emitted from one end side (+X side) of the emissionsurface 32 a of the liquid crystal display device 32 enters the lightentrance surface IS as a parallel light beam after passing through theprojection optical system 12, and is then reflected by the thirdreflecting surface 21 c, and then enters the first reflecting surface 21a of the light guide body member 21 s at the maximum reflection angleγ₊, and is then totally reflected. The image light GL42 is totallyreflected by the first and second reflecting surfaces 21 a, 21 b N−Mtimes (M denotes a natural number), for example, and then reaches theperipheral portion 23 m the nearest to the entrance (+X side) in theangle conversion section 423. The image light GL42 reflected by theperipheral portion 23 m is emitted in the direction forming an obtuseangle with respect to the +X axis so as to get away from the thirdreflecting surface 21 c at the entrance, and tilted by an angle θ₁₂(θ₁₂′ in the light guide device 420) with respect to the optical axis AX(see FIG. 14).

The image light GL43 emitted from the other end side (−X side) of theemission surface 32 a of the liquid crystal display device 32 enters thelight entrance surface IS as a parallel light beam after passing throughthe projection optical system 12, and is then reflected by the thirdreflecting surface 21 c, and then enters the first reflecting surface 21a of the light guide body member 21 s at the minimum reflection angleγ⁻, and is then totally reflected. The image light GL43 is totallyreflected by the first and second reflecting surfaces 21 a, 21 b N+Mtimes, for example, and then enters the peripheral portion 23 h thefurthest from the entrance (−X side) in the angle conversion section423. The image light GL43 reflected by the peripheral portion 23 h isemitted in the direction forming an acute angle with respect to the +Xaxis so as to be set back toward the third reflecting surface 21 c, andtilted by an angle θ₁₃ (θ₁₃′ in the light guide device 420) with respectto the optical axis AX (see FIG. 14).

As shown in FIG. 15, the angle conversion section 423 has a structurehaving a number of prisms 424 arranged in the X direction at apredetermined pitch. Each of the prisms 424 has a first junction surface424 j on the light exit side, and has a second junction surface 424 c onthe light entrance side. On the first junction surface 21 j of the lightguide body member 21 s or the body portion 20 a, and the first junctionsurface 424 j of each of the prisms 424, there is formed the half mirrorlayer 28 as a semi-transmissive reflecting film in a localized partialarea. The area where the half mirror layer 28 is formed is arranged tocorrespond to the partial area PA0 shown in FIG. 13B. In other words,the half mirror layer 28 is not formed in the exceptional area PAcomposed of the peripheral areas PA1, PA2. Similarly to the case shownin FIG. 8, the body portion 20 a, each of the prisms 424, and the lighttransmitting body member 23 s are bonded to each other with the bondinglayer CC in the partial area PA0 and the exceptional area PA.Specifically, the first junction surface 21 j, 424 j of the light guidebody member 21 s or the angle conversion section 423 and the secondjunction surface 424 c, 23 c of the angle conversion section 423 or thelight transmitting body member 23 s are bonded to each other via thebonding layer CC. It should be noted here that it is assumed thatregarding the junction having the half mirror layer 28 interveningtherein, the inner prism 424 i nearer to the light source out of thepair of prisms 424 adjacent to each other is regarded as a light guidemember, and the outer prism 424 o further from the light source isregarded as a light transmitting member.

According to the virtual image display device 100 of the fourthembodiment, since the half mirror layer (the semi-transmissivereflecting film) 28 provided to the light guide body member 21 s or theangle conversion section 423 is formed on the partial area PA0 of thefirst junction surface 21 j, 424 j, and the second junction surface 424c, 23 c of the angle conversion section 423 or the light transmittingbody member 23 s is bonded to the first junction surface 21 j, 424 j inat least the exceptional area PA in the light guide device 420, it ispossible to increase the bonding strength of the first junction surface21 j, 424 j and the second junction surface 424 c, 23 c, namely thestrength of the light guide device 420 composed of the light guide bodymember 21 s, the angle conversion section 423, and the lighttransmitting body member 23 s combined with each other even in the casein which the attachment force of the half mirror layer (thesemi-transmissive reflecting film) 28 with respect to the first junctionsurface 21 j, 424 j is not sufficiently strong.

The first junction surfaces 21 j, 424 j and the second junction surfaces424 c, 23 c are not limited to a smooth surface, but can be formed to bethe rough surface SR shown in FIG. 10, which can increase the bondingstrength by the bonding layer CC. Further, the first junction surfaces21 j, 424 j and the second junction surfaces 424 c, 23 c can also bearranged to be provided with the fitting shapes SF1, SF2 as therelatively coarse undulation shapes shown in FIG. 12, and it is possibleto align the light guide body member 21 s, the angle conversion section423, and the light transmitting body member 23 s with ease and relativeprecision before bonding.

It should be noted that the light guide body member 21 s, the angleconversion section 423, the light transmitting body member 23 s, and soon can be arranged to be covered by a hard coat layer. In other words,it is also possible to form the first and second reflecting surfaces 21a, 21 b, and so on by covering, for example, the surface of the bodyportion 20 a with the hard coat layer.

Fifth Embodiment

Hereinafter, a virtual image display device according to a fifthembodiment will be explained. It should be noted that the virtual imagedisplay device according to the present embodiment is a modified exampleof the virtual image display device 100 according to the firstembodiment, and is assumed to be the same as the virtual image displaydevice 100 according to the first embodiment unless particularlyexplained.

The virtual image display device 100 shown in FIGS. 16A through 16C isprovided with the image forming device 10 and a light guide device 520as a set. The light guide device 520 has a light guide member 521 as apart thereof. The light guide member 521 is provided with a body portion20 a and an angle conversion section 523 as an image take-out section.It should be noted that FIG. 16A corresponds to the A-A cross-section ofthe light guide member 521 shown in FIG. 16B.

The overall appearance of the light guide member 521 is formed by thebody portion 20 a, which is a flat plate extending in parallel to theX-Y plane in the drawings. Further, the light guide member 521 has thefirst reflecting surface 21 a, the second reflecting surface 21 b, andthe third reflecting surface 21 c as the side surfaces. Further, thelight guide member 521 also has the first side surface 21 e and thesecond side surface 21 f opposed to each other and contiguous to thefirst, second, and third reflecting surfaces 21 a, 21 b, and 21 c.Further, the light guide member 521 has a structure in which the prismsection PS is disposed as a part of the body portion 20 a at one endthereof in the longitudinal direction, and the angle conversion section523 composed of a number of micro mirrors embedded in the body portion20 a is disposed at the other end thereof in the longitudinal direction.Although the light guide member 521 is an integrated component, it ispossible to consider the light guide member 521 divided into the lightentrance section B1 the light guide section B2, and the light exitsection B3 (see FIG. 16C) similarly to the case of the first embodiment,and among these sections, the light entrance section B1 is a part havingthe third reflecting surface 21 c and the light entrance surface ISdescribed later, the light guide section 52 is a part having the firstand second reflecting surfaces 21 a, 21 b, and the light exit section B3is a part having the angle conversion section 523 and the light exitsurface OS described later.

The body portion 20 a is formed of a light transmissive resin materialor the like, and has the light entrance surface IS for taking in theimage light from the image forming device 10 and a light exit surface OSfor emitting the image light toward the eye EY of the observer on theplane on the reverse side opposed to the image forming device 10 or onthe observer side, the plane being parallel to the X-Y plane. The bodyportion 20 a has a rectangular tilted surface RS as a side surface ofthe prism section PS besides the light entrance surface IS, and on thetilted surface RS, there is formed a mirror layer 25 so as to cover thetilted surface RS. Here, the mirror layer 25 cooperates with the tiltedsurface RS to thereby function as the third reflecting surface 21 c,which is an incident light bending section, and disposed in the tiltedstate with respect to the light entrance surface IS. The thirdreflecting surface 21 c bends the image light, which enters from thelight entrance surface IS and proceeds in the +Z direction as a whole,so as to proceed in the −X direction deflected to the −Z direction as awhole to thereby surely combine the image light within the body portion20 a. Further, in the body portion 20 a, there is formed the angleconversion section 523 as a microstructure along the plane on thereverse side of the light exit surface OS. The body portion 20 a extendsfrom the third reflecting surface 21 c on the entrance side to the angleconversion section 523 on the back side, and guides the image light,which is input inside via the prism section PS, to the angle conversionsection 523.

The first and second reflecting surfaces 21 a, 21 b of the light guidemember 521 each totally reflect the image light bent by the prismsection PS or the light entrance section 81 as a pair of planes, whichare the principal surfaces of the body portion 20 a shaped like a flatplate, opposed to each other, and extend in parallel to the X-Y plane.The image light having been reflected by the third reflecting surface 21c firstly enters the first reflecting surface 21 a, and is then totallyreflected. Subsequently, the image light enters the second reflectingsurface 21 b, and is then totally reflected. By subsequently repeatingthe actions described above, the image light is guided to the back sideof the light guide device 520, namely the −X side where the angleconversion section 523 is disposed.

The angle conversion section 523 disposed so as to face the light exitsurface OS of the body portion 20 a is formed along an extended plane ofthe second reflecting surface 21 b and close to the extended plane inthe back side (−X side) of the light guide member 521. The angleconversion section 523 reflects the image light, which has been inputthereto via the first and second reflecting surfaces 21 a, 21 b of thelight guide member 521, at a predetermined angle to thereby bend ittoward the light exit surface OS. In other words, the angle conversionsection 523 converts the angle of the image light.

The image light emitted from the image forming device 10 and thenentering the light guide member 521 from the light entrance surface ISis evenly reflected and bent by the third reflecting surface 21 c, thenproceeds substantially along the optical axis AX in a condition ofhaving certain spread while being totally reflected by the first andsecond reflecting surfaces 21 a, 21 b of the light guide member 521 in arepeated manner, and is then further bent in the angle conversionsection 523 at an appropriate angle to thereby be in the state ready tobe taken out, and is then finally emitted to the outside from the lightexit surface OS. The image light emitted to the outside from the lightexit surface OS enters the eye EY of the observer as the virtual imagelight. By the virtual image light forming an image on the retina of theobserver, the observer can recognize the image light such as the picturelight due to the virtual image.

The light path of the image light in the light guide device 520 willhereinafter be explained. It should be noted that the light guide device520 in the fifth embodiment functions similarly to the light guidedevice 20 shown in FIG. 1A with respect to the vertical first directionD1 (the direction). In contrast, the light guide device 520 is arrangedto guide the image light with a number of propagation modes with respectto the horizontal second direction D2 (the X direction), and isdifferent from the light guide device 20 shown in FIG. 2A for guidingthe image light with the two propagation modes.

As shown in FIG. 16A, it is assumed that, out of the image light outputfrom the liquid crystal display device (the image light forming section)32 of the image display device 11, the component emitted from the centerportion of the emission surface 32 a indicated by the dotted line isimage light GL51, the component emitted from the right side (+X side) ofthe sheet of the emission surface 32 a indicated by the dashed-dottedline is image light GL52, and the component emitted from the left side(−X side) of the sheet of the emission surface 32 a indicated by thedashed-two dotted line is image light GL53.

The principal components of the respective image lights GL51, GL52, andGL53 having passed through the projection optical system 12 enter fromthe light entrance surface IS of the light guide member 521, and thenrepeat the total reflection on the first and second reflecting surfaces21 a, 21 b at respective angles different from each other. Specifically,among the image lights GL51, GL52, and GL53, the image light GL51emitted from the central portion of the emission surface 32 a of theliquid crystal display device (the image light forming section) 32enters the light entrance surface IS as a parallel light beam afterpassing through the projection optical system 12, and is then reflectedby the third reflecting surface 21 c, and then enters the firstreflecting surface 21 a of the light guide member 521 at a standardreflection angle γ₀, and is then totally reflected. Subsequently, theimage light GL51 repeats the total reflection on the first and secondreflecting surfaces 21 a, 21 b in a condition of keeping the standardreflection angle γ₀. The image light GL51 is totally reflected by thefirst and second reflecting surfaces 21 a, 21 b N times (N denotes anatural number), and then reaches the center portion 23 k of the angleconversion section 523. The image light GL51 reflected by the centralportion 23 k is emitted from the light exit surface OS in the directionof the optical axis AX perpendicular to the light exit surface OS or theX-Y plane as a parallel light beam.

The image light GL52 emitted from one end side (+X side) of the emissionsurface 32 a of the liquid crystal display device 32 enters the lightentrance surface IS as a parallel light beam after passing through theprojection optical system 12, and is then reflected by the thirdreflecting surface 21 c, and then enters the first reflecting surface 21a of the light guide member 521 at the maximum reflection angle γ₊, andis then totally reflected. The image light GL52 is totally reflected bythe first and second reflecting surfaces 21 a, 21 b N−M times (M denotesa natural number), for example, and then reaches the peripheral portion23 h the furthest from the entrance (−X side) in the angle conversionsection 523. The image light GL52 reflected by the peripheral portion 23h is emitted in the direction forming an acute angle with respect to the+X axis so as to be set back toward the third reflecting surface 21 c atthe entrance, and tilted by an angle θ₁₂ (θ₁₂′ in the light guide device520) with respect to the optical axis AX (see FIG. 17).

The image light GL53 emitted from the other end side (−X side) of theemission surface 32 a of the liquid crystal display device 32 enters thelight entrance surface IS as a parallel light beam after passing throughthe projection optical system 12, and is then reflected by the thirdreflecting surface 21 c, and then enters the first reflecting surface 21a of the light guide member 521 at the minimum reflection angle γ⁻, andis then totally reflected. The image light GL53 is totally reflected bythe first and second reflecting surfaces 21 a, 21 b N+M times, forexample, and then enters the peripheral portion 23 m the nearest to theentrance (+X side) in the angle conversion section 523. The image lightGL53 reflected by the peripheral portion 23 m is emitted in thedirection forming an obtuse angle with respect to the +X axis so as toget away from the third reflecting surface 21 c, and tilted by an angleθ₁₃ (θ₁₃′ in the light guide device 520) with respect to the opticalaxis AX (see FIG. 17).

It should be noted that as shown in FIG. 17, the angle conversionsection 523 is composed of a number of linear reflecting units 2 carranged in a stripe manner. In other words, the angle conversionsection 523 is configured by arranging a number of elongated reflectingunits 2 c, which extend in the Y direction, along a main light guidedirection along which the angle conversion section 523 extends, namelythe −X direction at a predetermined pitch PT. Each of the reflectingunits 2 c has a first reflecting surface 2 a and a second reflectingsurface 2 b as a set of reflecting surfaces, wherein the firstreflecting surface 2 a is one reflecting surface component disposed onthe back side, namely the downstream side of the light path, and thesecond reflecting surface 2 b is another reflecting surface componentdisposed on the entrance side, namely the upstream side of the lightpath, and the both reflecting surfaces 2 a, 2 b form a constant wedgeangle δ. Among these reflecting surfaces, at least the second reflectingsurface 2 b is a partial reflecting surface capable of transmitting someof the light, and enables the observer to observe the external image ina see-through manner. In the reflecting unit 2 c, the image lights GL52,GL53 are firstly reflected by the first reflecting surface 2 a on theback side, namely the −X side, and are then reflected by the secondreflecting surface 2 b on the entrance side, namely the +X side. Theimage lights GL52, GL53 having passed through the reflecting unit 2 care bent to have desired angles with only a single passage in the angleconversion section 523, and are then taken out to the observer sidewithout passing through any other reflecting units 2 c.

As shown in FIG. 18, the angle conversion section 523 has a structurehaving a bonding member 521 n extending from the light guide member 521and having a relatively thick plate-like shape, and a bonding member 523n extending from the light transmitting member 23 and having arelatively thin plate-like shape bonded to each other. The bondingmember 521 n has the first junction surface 21 j on the obverse side orthe external side, and the bonding member 523 n has the second junctionsurface 23 c on the reverse side or the observer side. On the firstjunction surface 21 j of the bonding member 521 n, there is formed thehalf mirror layer 28 as a semi-transmissive reflecting film in alocalized partial area. The area where the half mirror layer 28 isformed is arranged to correspond to the partial area PA0 shown in FIG.16B. In other words, the half mirror layer 28 is not formed in theexceptional area PA composed of the peripheral areas PA1, PA2. Similarlyto the case shown in FIG. 8, the bonding member 521 n of the light guidemember 521 and the bonding member 523 n of the light transmitting member23 are bonded to each other with the bonding layer CC in the partialarea PA0 and the exceptional area PA. In other words, the first junctionsurface 21 j of the bonding member 521 n and the second junction surface23 c of the bonding member 523 n are bonded to each other via thebonding layer CC.

According to the virtual image display device 100 of the fifthembodiment, since the half mirror layer (the semi-transmissivereflecting film) 28 provided to the bonding member 521 n of the lightguide member 521 is formed on the partial area PA0 of the first junctionsurface 21 j, and the second junction surface 23 c of the angleconversion section 523 is bonded to the first junction surface 21 j inat least the exceptional area PA in the light guide device 520, it ispossible to increase the bonding strength of the first junction surface21 j and the second junction surface 23 c, namely the strength of thelight guide device 520 composed of the light guide member 521 and thelight transmitting member 23 combined with each other even in the casein which the attachment force of the half mirror layer (thesemi-transmissive reflecting film) 28 with respect to the first junctionsurface 21 j is not sufficiently strong.

The first junction surface 21 j and the second junction surface 23 c arenot limited to a smooth surface, but can be formed to be the roughsurface SR shown in FIG. 10 and so on, which can increase the bondingstrength by the bonding layer CC. Further, the first junction surface 21j and the second junction surface 23 c can also be arranged to beprovided with the fitting shapes SF1, SF2 as the relatively coarseundulation shapes shown in FIG. 12, and it is possible to align thelight guide member 521 and the light transmitting member 23 with easeand relative precision before bonding.

Other Issues

Although the invention is hereinabove explained along the embodiments,the invention is not limited to the embodiments described above, but canbe put into practice in various forms within the scope or the spirit ofthe invention, and the following modifications, for example, are alsopossible.

Although in the above explanation the first junction surface 21 j andthe second junction surface 23 c are bonded to each other in the partialarea PA0 and the exceptional area PA, it is also possible to bond thefirst junction surface 21 j and the second junction surface 23 c to eachother only in the exceptional area PA. In this case, it is possible toperform bonding in the entire exceptional area PA, and it is alsopossible to perform bonding in a plurality of bonding areas provided tothe exceptional area PA.

Although in the above explanation it is assumed that the half mirrorlayer (the semi-transmissive reflecting film) 28 is formed in thehorizontally long rectangular area, the contour of the half mirror layer28 can arbitrarily be changed in accordance with the specifications suchas the purpose. It should be noted that it is desirable for the halfmirror layer 28 to sufficiently cover the effective area EA.

Although in the above explanation the light guide member 21 and thelight transmitting member 23 are coupled in series on each other, it isalso possible to fix the first and second side surfaces 21 e, 21 f ofthe light guide member 21 with the frame member extending from the lighttransmitting member 23 in a reinforcing manner.

Although in the above explanation the transmissive liquid crystaldisplay device 32 and so on are used as the image light forming section,the image light forming section is not limited to the transmissiveliquid crystal display device, but a variety of devices can be used. Forexample, the configuration using the reflective liquid crystal displaydevice is also possible, and it is also possible to use the digitalmicromirror Device™ and so on instead of the liquid crystal displaydevice 32. Further, it is also possible to use a light emitting displaydevice such as an organic EL device instead of the liquid crystaldisplay device.

Although in the embodiments described above directionality is notparticularly provided to the illumination light SL from the illuminationdevice 31, it is possible to provide the directionality corresponding tothe location of the liquid crystal display device 32 to the illuminationlight SL. Thus, it is possible to efficiently illuminate the liquidcrystal display device 32, and the luminance variation due to thelocation of the image light GL can be reduced.

Although in the above explanation, the light entrance surface IS and thelight exit surface OS are disposed on the same plane, the configurationis not limited thereto, but the configuration of disposing the lightentrance surface IS on the same surface as the first reflecting surface21 a, and the light exit surface OS on the same surface as the secondreflecting surface 21 b, for example, can also be adopted. In this case,it results that the first reflecting surface 21 a and the fourthreflecting surface 21 d form an obtuse angle.

Although in the above explanation, the light guide member 21 extends inthe lateral direction along which the eyes EY are arranged, it ispossible to arrange that the light guide member 21 extends in a verticaldirection. In this case, it results that the optical panels 110 shown inFIG. 1, namely the light guide members 21, 421, 521, are not disposedserially but disposed in parallel to each other.

Although in the above explanation, the light guide device 20, 420, 520provided with the light entrance section B1, the light guide section B2,and the light exit section B3 is used, in the light entrance section B1and the light exit section B3, it is not necessary to use a flat mirroror a flat half mirror as the half mirror layer 28 and so on, but it isalso possible to provide a function like a lens by adopting a curvedmirror having a spherical shape or a aspherical shape. Further, it isalso possible to dispose a hologram element as an imaginarysemi-transmissive mirror instead of the half mirror layer 28. In thiscase, the hologram element is also included in the semi-transmissivereflecting surface in a broad sense. It should be noted that it is alsopossible to add an optical function such as light collection to such ahologram element.

Further, as shown in FIG. 19, a prism or a block-like relay member 1025separated from the light guide section B2 can be used as the lightentrance section B1, and it is also possible to provide a function likea lens to an entrance/exit surface and a reflective inner surface of therelay member 1025. It should be noted that although a light guide body26 constituting the light guide section B2 is provided with the firstand second reflecting surfaces 21 a, 21 b for making the image light GLpropagate with reflection, these reflecting surfaces 21 a, 21 b are notrequired to be parallel to each other, but can be formed to have acurved shape. The light guide body 26 shown in FIG. 19 is bonded to thelight transmitting member 23, and the junction section of the lightguide body and the light transmitting member is provided with the halfmirror layer 28. Also in this case, similarly to the case of the firstembodiment, by bonding the light guide body 26 and the lighttransmitting member 23 to each other in at least the exceptional area inthe periphery of the half mirror layer 28, the bonding strength betweenthe light guide body 26 and the light transmitting member 23 can beincreased, and thus the strength of the light guide device 20 can beincreased.

Although in the explanation described above the specific explanation ispresented assuming that the virtual image display device 100 is thehead-mount display, it is also possible to modify the virtual imagedisplay device 100 into a head-up display.

Although the virtual image display device 100 according to theembodiments described above has a configuration of providing the displaydevices 100A, 1003 (each including specifically the image forming device10, the light guide device 20, and so on) corresponding respectively tothe right eye and the left eye, it is also possible to adopt aconfiguration of providing the image forming device 10 and the lightguide device 20 corresponding to either one of the right and left eyesto thereby view the image with a single eye.

Although in the embodiments described above, it is assumed that thefirst optical axis AX1 passing through the light entrance surface IS andthe second optical axis AX2 passing through the light entrance surfaceIS are parallel to each other, it is also possible to make these opticalaxes AX1, AX2 non-parallel to each other.

Although in the embodiments described above the display luminance of theliquid crystal display device 32 is not particularly adjusted, it ispossible to perform adjustment of the display luminance in accordancewith the ranges and the overlap of the projection images IM1, IM2 shownin FIG. 6B.

Although in the embodiments described above the reflectance of the halfmirror layer 28 provided to the fourth reflecting surface 21 d of thelight guide member 21 is set to 20% to thereby give priority tosee-through image, it is also possible to set the reflectance of thehalf mirror layer 28 to not lower than 50% to thereby give priority tothe image light. It should be noted that the half mirror layer 28 can beformed on the second junction surface 23 c of the light transmittingmember 23.

Although in the above explanation it is assumed that in the first andsecond reflecting surfaces 21 a, 21 b, the image light is totallyreflected by the interface with air to thereby guide the image lightwithout providing a mirror or a half mirror on the surfaces, the totalreflection in the invention includes the reflection performed by themirror coat or the half mirror film formed on the entire or a part ofeach of the first and second reflecting surfaces 21 a, 21 b. Forexample, there is included the case in which the mirror coat or the likeis applied to the entire or a part of each of the first and secondreflecting surfaces 21 a, 21 b with the incident angle of the imagelight fulfilling the total reflection condition, thereby reflecting thesubstantially whole image light. Further, it is also possible to coatthe entire or a part of each of the first and second reflecting surfaces21 a, 21 b with a mirror having some transmissive property providing theimage light with sufficient brightness can be obtained.

Further, in the explanation of the fourth and fifth embodiments, thepitch PT of the arrangement of the reflecting units 2 c constituting theangle conversion section 423, 523 is not limited to the case in whichthe pitch PT is constant throughout the first reflecting surface 2 a,but includes the case in which the pitch PT has a certain variation.

Although in the above explanation the mirror layer 25 constituting theprism section PS and the tilt angle of the tilted surface RS are notparticularly mentioned, the tilt angle of the mirror layer 25 and so onwith respect to the optical axis AX can be set to various values inaccordance with the specifications such as the purpose.

Although in the explanation of the fourth and fifth embodimentsdescribed above the V-shaped groove formed with the reflecting unit 2 cis shown as if the tip thereof is in the pointed state, the shape of theV-shaped groove is not limited thereto, but can be one having the tipcut flatly or one having the tip provided with a round shape.

The entire disclosure of Japanese Patent Application No. 2011-216712,filed Sep. 30, 2011 is expressly incorporated by reference herein.

What is claimed is:
 1. A virtual image display device comprising: animage display device adapted to form an image light; a projectionoptical system adapted to form a virtual image by the image lightemitted from the image display device; a light guide member including alight entrance section adapted to take in the image light having passedthrough the projection optical system, a light guide section adapted toguide the image light taken in from the light entrance section usingtotal reflection by a first surface and a second surface opposed to eachother, and a light exit section adapted to take out the image lighthaving passed through the light guide section; and a light transmittingmember adapted to make observation of external light possible by beingbonded to the light guide member, wherein the light guide member has asemi-transmissive reflecting film, which bends the image light andtransmits the external light, disposed on a partial area of a firstjunction surface bonded to the light transmitting member, thesemi-transmissive reflecting film not being disposed on an area of thefirst junction surface other than the partial area, and the lighttransmitting member has a second junction surface opposed to the firstjunction surface including an exceptional area, the exceptional areabeing disposed to the area of the first junction surface other than thepartial area, and the light transmitting member being bonded to thefirst junction surface with an adhesive in at least the exceptionalarea.
 2. The virtual image display device according to claim 1, whereinat least one of the exceptional area of the first junction surface andan opposed area of the second junction surface corresponding to theexceptional area includes a nonsmooth surface having an undulation. 3.The virtual image display device according to claim 2, wherein thenonsmooth surface is a rough surface provided with a fine undulation bya roughening process.
 4. The virtual image display device according toclaim 2, wherein the nonsmooth surface provided to the first junctionsurface and the nonsmooth surface provided to the second junctionsurface fit each other.
 5. The virtual image display device according toclaim 2, wherein the nonsmooth surface provided to the first junctionsurface and the nonsmooth surface provided to the second junctionsurface have undulation shapes reverse to each other.
 6. The virtualimage display device according to claim 1, wherein in the first junctionsurface of the light guide member, the partial area adapted to supportthe semi-transmissive reflecting film is arranged in a central portionof the first junction surface with respect to a predetermined direction,and the exceptional area in a periphery of the semi-transmissivereflecting film corresponds to a peripheral area sandwiching the partialarea on both ends in the predetermined direction.
 7. The virtual imagedisplay device according to claim 6, wherein the first junction surfaceis bonded to the second junction surface as a whole, and the peripheralarea is the nonsmooth surface as a whole.
 8. The virtual image displaydevice according to claim 1, wherein the light guide member has thelight entrance section, the light guide section, and the light exitsection as an integrated member, the light entrance section has a thirdreflecting surface as a plane forming an obtuse angle with respect toeither one of the first reflecting surface and the second reflectingsurface, and the first junction surface of the light exit section has afourth reflecting surface as a plane forming an obtuse angle withrespect to either one of the first reflecting surface and the secondreflecting surface.
 9. The virtual image display device according toclaim 1, wherein the light guide member, the light transmitting member,and the adhesive are formed of respective materials having roughly thesame refractive indexes.
 10. The virtual image display device accordingto claim 1, wherein the semi-transmissive reflecting film is disposedonly on a partial area of a first junction surface to be bonded to thelight transmitting member.
 11. The virtual image display deviceaccording to claim 1, a transmittance of external light though thesemi-transmissive area being higher than a reflectance of the imagelight on the semi-transmissive area.